CTC187 HOT shorting out

[JohnAce]

I have a CTC187n in for repair. It had a blown HOT and after repalceing the
flyback was sparking. I replaced the flyback and transistor. Soldered the the
bad connection on the driver (which were not bad) and other area's on the
board. The set plays for about 30 seconds to maybe a few minutes before
shorting out again. (high pitch) I feel no overheating parts before this
happens. And voltages are preetty much to were they are suppose to be. This
uses a BUH517 for a transistor and it is a 36" set .. Any tip were to look?
THanks

 

[Jason D.]

On 25 Oct 2003 01:08:14 GMT, johnace@aol.com (JohnAce) wrote:

I have a CTC187n in for repair. It had a blown HOT and after repalceing the
flyback was sparking. I replaced the flyback and transistor. Soldered the the
bad connection on the driver (which were not bad) and other area's on the
board. The set plays for about 30 seconds to maybe a few minutes before
shorting out again. (high pitch) I feel no overheating parts before this
happens. And voltages are preetty much to were they are suppose to be. This
uses a BUH517 for a transistor and it is a 36" set .. Any tip were to look?
THanks

Check all the grounds (micro & tuner), check that 2.4K SMD resistor
emitter on that HOT driver circuit; I had this once before (2 weeks
ago, did it on hunch when I heard of this tip but didn't realize).
Remove & scrape clean all 5 pins on the HOT driver transformer.

ESR the capacitors around the SMPS, one small cap (10uF 68V) in
flyback secondaries. I find them high in ESR because of heat from
SMPS transformer and heatsinks.

Be sure this extra work is worth it because these chassis is rather
old therefore the CRT quality. Is pix "EXCELLENT"?

BTW, use exact RCA originals for fly & HOT, thinly grease that HOT's
heatsink contact for best thermal transfer. Before applying that
grease, did the lead forming by test fitting for flat contact with
heatsink with leads loose in the through holes?

Cheers,

Wizard

 

[Vince and Marge]

check out the safety caps
Vince
"JohnAce" <johnace@aol.com> wrote in message
news:20031024210814.14735.00000070@mb-m20.aol.com...

I have a CTC187n in for repair. It had a blown HOT and after repalceing
the
flyback was sparking. I replaced the flyback and transistor. Soldered the
the
bad connection on the driver (which were not bad) and other area's on the
board. The set plays for about 30 seconds to maybe a few minutes before
shorting out again. (high pitch) I feel no overheating parts before this
happens. And voltages are preetty much to were they are suppose to be.
This
uses a BUH517 for a transistor and it is a 36" set .. Any tip were to
look?
THanks

 

[Jason D.]

On Fri, 24 Oct 2003 22:49:55 -0600, "Vince and Marge"
<vmschmitt@charter.net> wrote:

check out the safety caps
Vince

Interesting...

I hear many names for those horizontal circuit capacitors, like this
one and damper caps, etc.

Which caps is really the "safety" and other damper caps goes in where?

Schematics and training manuals for specific chassis doesn't mention
those. Is there a book or like this that have those terms?

Cheers,

Wizard